Why is the winter sky so beautiful?

Well. Mainly, because there are so many bright stars visible in wintertime - far more than in the summer. And this, despite the fact that we enjoy the glorious star clouds of Cygnus, Sagittarius, and Scorpius during the hotter months. But let's face it, the individual stars making up those constellations are not, pound for pound, the equal of those composing Orion, Gemini, or Auriga... not to mention glorious Sirius, Procyon, or Aldebaran.

So why are there so many more brilliant stars up there in the winter? To understand why, we need to know a bit about the geography (so to speak) of our galaxy, and our place in it.

Take a look at the above illustration. Although the matter is not "settled science"just yet, there is broad consensus that the Milky way is composed of a nucleus, four spiral arms, and an uncertain number of "spurs" (broken off pieces of spiral arms). Our sun happens to be located on the inner (that is, closer to the galactic center) edge of the Orion Spur. Between us and the galactic core are no less than three spiral arms, the closest being the Carina-Sagittarius Arm. But when we look in that direction (in the summertime), our gaze has to first traverse many thousands of light years just to get to even the closest, or Sagittarius, Arm. So no matter how intrinsically bright any stars are in that direction, they're going to look dimmer just from sheer distance.

Not so in wintertime! We are smack up against the Orion Spur, and the blue-white or red supergiants in that direction are therefore that much closer. So it's mainly a cosmic optical illusion. The winter sky does not boast a greater number of bright stars - it's just that those that happen to be in that direction are significantly closer to us.

But who cares? Get out there and enjoy the spectacle of the glorious winter sky!